Comparison of Optical Coherence Tomography-derived Minimal Lumen Area, Invasive Fractional Flow Reserve and FFRCT

Inclusion Criteria: * Unprotected LM lesion \[midshaft, and distal bifurcation (Medina 1,1,1 or 1,1,0 or 1,0,1 or 1,0,0)\] of 30% to 80% angiographic diameter stenosis (DS) on visual estimation or equivocal disease by angiography. * Age ≥18 years. * Ability to give preliminary oral consent witnessed by an independent physician or sign written informed consent prior to any study-specific procedures. Exclusion Criteria: * Significant distal lesions (\>50% angiographic DS on visual estimation within the left anterior descending artery \[LAD\] or left circumflex artery \[LCX\], except for ostium of LAD or LCX or diseased side branch \[e.g. diagonal branch, obtuse marginal branch\]) * Ostial LM disease. * Acute coronary syndrome (ACS) (non-ST-elevation ACS and ST-elevation MI). * LM In-stent restenosis. * Previous coronary stenting of the left coronary system. * Chronic total occlusion. * Previous coronary artery bypass graft. * Previous MI related to the left coronary artery. * Occurrence of ventricularization or hypotension during engagement of the LM ostial lesion. * The presence of hemodynamic instability. * Known renal insufficiency (serum creatinine \>1.5mg/dL or receiving dialysis). * Female of childbearing potential (age \<50 years and last menstruation within the last 12 months), who did not undergo tubal ligation, ovariectomy or hysterectomy. * Life expectancy less than 1 year. * Contraindication or known allergy against protocol-required medications including heparin, iodinated contrast, β-blocker, nitroglycerin, and adenosine. * Body mass index \>35kg/m2. * Complex congenital heart disease other than anomalous coronary origins alone. * Ventricular septal defect.